1. Field of the Invention
The present invention relates generally to the field of quality control testing, and more particularly to an apparatus and method for testing semiconductor device packages for abrasion resistance.
Semiconductor devices are typically encapsulated in a plastic or ceramic material in order to protect the device from damage. The resulting structures, referred to hereinafter as semiconductor device packages, have conductive leads brought out through the protective material and are typically mounted on printed circuit boards in building larger electronic systems.
Semiconductor device packages are usually marked to identify the particular device which has been encapsulated. Information such as the manufacturer, the type of device, the identity of the electrical leads, and the like, will be imprinted on the package in a permanent manner. It is important that the printed information remain on the package, and steps are taken to assure that the markings will not be lost even in hostile environments.
To assure the adequacy of the package markings, certain quality control tests have been devised. In particular, methods 5005 and 2015 of Military Standard 883 (MIL-STD-883) call for immersing the semiconductor devices in various solvents and thereafter brushing the outer surface of the package and examining the package for damage. If the package is damaged in any way, particularly if the markings are missing in whole or in part, faded, smeared, blurred, or dislodged, the packages has failed the quality control test.
In any quality testing, such as that specified by MIL-STD-883, it is critically important that the testing be carried out in a highly repeatable manner. Each step of the testing must be performed pursuant to specific parameters, and deviations from these parameters individual tests must be avoided. Any step which cannot be precisely controlled, such as steps which require subjective human judgement, will introduce error and non-repeatability into the test.
As heretofore carried out, the brushing step performed under MIL-STD-883 has been accomplished manually. Such manual brushing can lead to widely varying results. A package which sustains no damage when lightly brushed, might well be harmed by more vigorous treatment. Conversely, few packages would be able to withstand the onslaught of a determined individual wielding a brush.
For these reasons, it would be desirable to provide an apparatus and method for uniformly testing semiconductor device packages. In particular, it would be desirable to provide an automated system which eliminates human judgement from the brushing step of the above-described testing procedure and which produces repeatable results.
2. Description of the Prior Art
The patent literature reveals a number of devices intended to test the effect of mechanical abrasion on various articles. See, e.g., U.S. Pat. No. 4,196,611 to Suga; U.S. Pat. No. 2,966,790 to Walker; U.S. Pat. No. 2,950,617 to Campbell; U.S. Pat. No. 2,929,240 to Williams, U.S. Pat. No. 2,734,375 to Galbraith et al.; U.S. Pat. No. 2,590,839 to Clapham; and U.S. Pat. No. 2,519,556 to Fish. None of these patents disclose the use of a reciprocating brush under constant load for abrasion testing.
A number of devices employing rotary brushes for cleaning glass, bottles and the like have been proposed. See, e.g., U.S. Pat. No. 2,636,199 to Stanton, et al.; U.S. Pat. No. 1,921,680 to Kopnicky; U.S. Pat. No. 957,301 to Buchheit; U.S. Pat. No. 876,706 to Failing; U.S. Pat. No. 787,858 to Schafer; U.S. Pat. No. 583,283 to Donally; U.S. Pat. No. 518,275 to Rantz; and U.S. Pat. No. 490,682 to Roemer. None of these patents disclose devices having reciprocating brushes under constant load suitable for abrasion testing.